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Another Silly General Question (Villiers Engine) #782717 08/27/19 2:04 am
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Geoff Online Content OP
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Upon attempting to insert my gudgeon pin into the piston I have discovered I cant. This is after heating piston and and the small end of the conrod with a heat gun - and cooling the pin off with liquid Nitrogen. Pin only goes in on one side, and then only half way into the piston (it does not actually go through - even with some "mechanical persuasion").

Am I missing something obvious as this is the first time I have done this, or is the pin just fubar? At this point I am getting ready to splurge on a new piston kit for the motor, but would like some reassurance that the answer / method is not right in front of me. The piston / pin / rings / etc... has an unknown provenance. This is on a Villiers 32A.

Thanks in advance,

Geoff


'78 T140V
'74 Commando
'69 TR6R
'67 Starfire
'64 Greeves TES
'58 Allstate (Puch) 175
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Re: Another Silly General Question (Villiers Engine) [Re: Geoff] #782722 08/27/19 2:57 am
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Rohan Offline
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Is this for your Greeves, or something else ?
Did the pin come with the piston, or separately.
And has it ever been in the piston at any point in its life. ?
Does the piston look intact and undamaged an undistorted ?

How hot did you get stuff . ?
The procedure for Norton pistons is to put a hot iron (of the ironing board type)
on it, and let it stay for minutes. This gets thing surprising hot - and evenly hot.
The piston does have to be flat topped for this to work though.

Still no go ?
The usual course of action at this point is out with the micrometer.
Have a careful measure of each end of the gudgeon pin, and in the middle.
What you are looking for is if it is worn or tapered at any point.
Will it go into one side of the piston, or both, or only partly either side ?

If its mismatched parts, and only not going in by a mere trace, it is permissible
to give the gudgeon pin a very slight easing - either by something like emery cloth
or maybe even valve grinding paste. Be sure to remove every last trace before introducing
it to the piston, since abrasive particles can embed themselves in the alloy.

Best not to work on the piston, since if its a standard size you may be able to track down a suitable
another gudgeon pin, if the above doesn't succeed.
hopethishelpsabit.

Re: Another Silly General Question (Villiers Engine) [Re: Geoff] #782724 08/27/19 3:05 am
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Wilfred Online Content
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Geoff

From recent experience, I would probably not use that piston unless you can get the holes for the gudgeon pin honed or reamed to give you a good fit.

After rebuilding my 67 T100 engine 3 or 5 years ago, I have had the pleasure of one of the pistons seizing as soon as the engine was doing any work at all. Had it apart, rehoned to get the alloy out of the barrel, installed new rings, checked the clearances, put it back together after checking everything else and it seized again and again. So then I took the engine all apart and took the whole plot down to a friend who is a machinist and a Brit bike restorer and still a fine trials rider to boot. After checking everything, he decided the problem was that one the NOS Hepolite pistons was incorrectly honed for the wrist pin/gudgeon pin and this wouldn't allow the piston to expand correctly in the wrist pin area so would expand instead front and rear with the resulting seizures. My parts supplier had neve heard about this problem and did a search and, voila, found the info about Triumph going to Hepolites and experiencing seizures because of the wrist pin holes.

So now it's a pair of little used pistons that don't have tight gudgeons and we'll try again. As I thought back to the last time I took it apart, the right piston with the heat of the hair drier had an easy wrist pin removal while the left one, even with the heat, was still in need of a fair amount of help to get it out. Another clue was the nice colour of the ends of the pin where the heat had built up. As my friend told me, it's important that the gudgeon is floating in the piston for proper expansion when warmed up.

Sorry for the long explanation. The whole thing makes sense so here's hoping that my rebuild will now result in more long and trouble free rides.

With all you've done to try to install yours, I would think that something is very wrong and further investigations would surely be needed. Someone else on the Forum will certainly have more/better advice as this is just my experience.

Cheers, Wilf


"It's about the ride..."
Re: Another Silly General Question (Villiers Engine) [Re: Geoff] #782729 08/27/19 3:57 am
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Rohan Offline
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Villiers engines are usually as tough as old boots !
So unless that piston is of recent manufacture, it should be 100 %.
As long as there is some oil in the petroil - which makes it entirely unlike Triumphs ?!

Not that I have a lot of actual experience with that particular variety, but they have been around for quite a while...
https://live.staticflickr.com/4133/4963932042_fb1ffd5ef2_b.jpg

Re: Another Silly General Question (Villiers Engine) [Re: Geoff] #782741 08/27/19 7:49 am
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triton thrasher Online Content
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The Triumph thing: when Triumph changed to Hepolite pistons, bigger clearances than for the in-house low expansion pistons were (and are) required. I think it was as simple as that.


Amateur Loctite enthusiast.
Re: Another Silly General Question (Villiers Engine) [Re: Geoff] #782742 08/27/19 7:55 am
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triton thrasher Online Content
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Are you working from a manual?

New small end bushes often have to be reamed to size.


Amateur Loctite enthusiast.
Re: Another Silly General Question (Villiers Engine) [Re: Geoff] #782754 08/27/19 2:56 pm
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Geoff Online Content OP
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This is for my Greeves.

The prior owner went through and replaced the con rod. The piston is +0.010. Not sure if its old or new (Villiers Spares sells in increments of 0.020). I had to beat the pin out. The pin looks like it may have been around for a while. One bushing looks distorted, and will not accept the pin at all, the other side only half way through.

At this juncture, I think you all have made my mind clear, and I will go for a new piston setup. smile

Last edited by Geoff; 08/27/19 2:57 pm.

'78 T140V
'74 Commando
'69 TR6R
'67 Starfire
'64 Greeves TES
'58 Allstate (Puch) 175

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